Gutter assemblies for collecting the drainage from the valley formed by two adjacent roof sections of a building are well known in the art. Typical assemblies of this type are shown in Stephenson U.S. Pat. No. 3,735,596, Beals U.S. Pat. No. 3,264,790 and Colby U.S. Pat. No. 2,736,397. Gutter assemblies of this type comprising cooperating primary gutters and secondary, or backup, gutters extending beneath the primary gutters are also well known in the art, being shown, for example, in Rice U.S. Pat. No. 884,208, Weston U.S. Pat. No. 870,917 and Hippard U.S. Pat. No. 696,043.
A major deficiency of valley gutters of the prior art, including systems having a secondary gutter, is their susceptibility to leakage occasioned by thermal expansion or contraction. In contrast to the principal structural members of a building, which are thermally insulated from the exterior and remain approximately at room temperature, the valley gutter is directly exposed to the exterior and thus experiences appreciable thermal expansion or contraction relative to the adjacent structural portions of the roof. If the gutter is formed as a single integral member, either by starting with a single elongated gutter trough or by welding several shorter troughs together, all of the expansion or contraction of the gutter will occur at its ends, with the result that the gutter will inevitably tear loose from the adjacent building walls.
An alternative construction is to form the gutter of several telescoping sections, so as to reduce the relative expansion or contraction of the ends of any one section, and to use a sealant such as mastic at the joints between sections to minimize leakage. While this alternative form of construction preserves the watertight integrity of the gutter at its ends adjacent the building walls, it does so only by increasing the possibility of leakage along the length of the gutter, owing to the impossibility of maintaining a perfect seal at the joints. Nor does providing a secondary gutter beneath the primary gutter overcome these problems of the prior art. Like the primary gutter, the secondary gutter will either pull away from the building walls at its ends or suffer leakage at intermediate joints, depending on the mode of construction.
Barlow U.S. Pat. No 4,129,967 discloses a system for collecting fluid seepage through expansion joints between adjacent building slabs in which a flexible receiving member is disposed along the underside of the regions between the slabs. Since the receiving member is simply suspended from the building slabs and is supported only at its upper edges, it cannot hold any appreciable amount of seepage without risking the possibility of rupture or of separation from the slabs.